Internal combustion engines balance shaking forces resulting from crankshaft and connecting rod assembly rotation. The balance shaft is operable to offset rotational energy created by the rotation of the crankshaft. Both the camshaft and balance shaft are typically driven by gears, or sprockets. A crankshaft gear drives both the camshaft gear and the balance shaft gear, often using belts or chains. Unfortunately, belts or chains may break and often require tensioners. Tensioners add to the complexity, and cost, of building or repairing engines. In addition, tensioners may be remotely located and tensioner placement can result in parasitic energy losses.
Each gear rotates at a speed inversely proportional to its relative radius compared to the crankshaft gear. For example, if camshaft gear radius is twice the radius of the crankshaft gear, the camshaft will rotate at half the speed of the crankshaft gear. Similarly, balance shaft gear rotates at twice the speed of the crankshaft gear, if the radius of the balance shaft gear is half the radius of the crankshaft gear.